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排序方式: 共有195条查询结果,搜索用时 31 毫秒
61.
62.
Dr. Veronika Novakova Miroslava Lásková Hana Vavřičková Dr. Petr Zimcik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14382-14392
Tetrapyrazinoporphyrazines (TPyzPzs) bearing one, two, four or eight 3,5‐di(tert‐butyl)‐4‐hydroxyphenol moieties were synthesized as zinc(II) complexes and metal‐free derivatives. The deprotonation of the phenol using tetrabutylammonium hydroxide induced the formation of a strong donor for intramolecular charge transfer that switched OFF the red fluorescence (λF~660 nm) of the parent zinc TPyzPzs. The changes were fully reversible for TPyzPzs with one to four phenolic moieties, and an irreversible modification was observed for TPyzPzs substituted with eight phenols. The sensors were anchored to lipophilic particles in water, and a pKa approximately 12.5–12.7 was determined for the phenolic hydroxyl based on fluorescence changes in different buffers. In addition, a novel concept for fluorescence OFF‐ON‐OFF switching in metal‐free TPyzPzs bearing phenolic moieties upon addition of specific amounts of base was demonstrated. 相似文献
63.
Zuzana Barbieriková Maroš Bella Ľudmila Sekeráková Jozef Lietava Miroslava Bobeničová Dana Dvoranová Viktor Milata Jana Sádecká Dominika Topoľská Tomáš Heizer Roman Hudec Adriana Czímerová Soňa Jantová Vlasta Brezová 《Journal of Physical Organic Chemistry》2013,26(7):565-574
7‐R‐9‐ethyl‐6,9‐dihydro‐6‐oxo‐[1,2,5]selenadiazolo[3,4‐h]quinolines (R = H, COOC2H5, COOCH3, COOH and COCH3, E1h , E2h , E3h , E4h , E5h ) and 6‐ethyl‐6,9‐dihydro‐9‐oxo‐[1,2,5]selenadiazolo[3,4‐f]quinoline ( E1f ) were characterized by UV/vis, FT‐IR and fluorescence spectroscopy. The electronic absorption spectra of the derivatives E1h , E2h , E3h and E5h in the aprotic solvents dimethylsulfoxide (DMSO) and acetonitrile (ACN) reveal low‐energy absorption maxima with λmax > 400 > nm, shifted hypsochromically in water. In DMSO, N‐ethyl selenadiazoloquinolones behave as strong fluorescent agents (λem ≥ 550 nm) with the exception of the carboxylic acid derivative E4h which shows only poor emission. Photoinduced reactions of N‐ethyl selenadiazoloquinolones were investigated by means of electron paramagnetic resonance (EPR) spectroscopy. Photoexcitation of N‐ethyl selenadiazoloquinolones in aerated DMSO with either 385 nm or 400 nm wavelengths, monitored by EPR spin trapping technique, results in the generation of superoxide radical anions; under an inert atmosphere, the generation of methyl radicals originating from the solvent predominates. Upon exposure at either 365 nm, 385 nm or 400 nm, aerated ACN solutions of selenadiazoloquinolones in the presence of sterically hindered amines produce nitroxide radicals via a reaction with photogenerated singlet oxygen. The 7‐substituted derivatives of 9‐ethyl‐6,9‐dihydro‐6‐oxo‐[1,2,5]selenadiazolo[3,4‐h]quinoline behave as photosensitizers activating molecular oxygen upon photoexcitation and possess the sufficient photochemical stability under the given experimental conditions. The cytotoxic effects of non‐photoactivated and UVA photoactivated N‐ethyl substituted selenadiazoloquinolones on cancer (human HeLa and murine L1210) and non‐cancer (NIH‐3T3) cell lines were monitored by the MTT test. The derivative E2h demonstrates the highest cytotoxic/photocytotoxic activity on the neoplastic cell lines. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
64.
A new regioselective synthesis of 5- and 6-aryluracil bases based on direct C-H arylations of diverse 1,3-protected uracils has been developed. Benzyl-protected uracils were selected as the most practical in terms of stability during the arylation and facile cleavage of the benzyl groups. Pd-catalyzed C-H arylations in the absence of CuI gave preferentially 5-aryl-, whereas the reactions in the presence of CuI gave 6-aryl-1,3-dibenzyluracils. Final deprotection either by transfer hydrogenolysis over Pd/C or by treatment with BBr(3) gave the desired free arylated uracil bases in good yields. 相似文献
65.
Salehi-Reyhani A Kaplinsky J Burgin E Novakova M deMello AJ Templer RH Parker P Neil MA Ces O French P Willison KR Klug D 《Lab on a chip》2011,11(7):1256-1261
We have developed a generic platform to undertake the analysis of protein copy number from single cells. The approach described here is 'all-optical' whereby single cells are manipulated into separate analysis chambers using an optical trap; single cells are lysed by a shock wave caused by laser-induced microcavitation, and the protein released from a single cell is measured by total internal reflection microscopy as it is bound to micro-printed antibody spots within the device. The platform was tested using GFP transfected cells and the relative precision of the measurement method was determined to be 88%. Single cell measurements were also made on a breast cancer cell line to measure the relative levels of unlabelled human tumour suppressor protein p53 using a chip incorporating an antibody sandwich assay format. These results suggest that this is a viable method for measuring relative protein levels in single cells. 相似文献
66.
Comparison of various easy-to-use procedures for extraction of phenols from apricot fruits 总被引:1,自引:0,他引:1
Zitka O Sochor J Rop O Skalickova S Sobrova P Zehnalek J Beklova M Krska B Adam V Kizek R 《Molecules (Basel, Switzerland)》2011,16(4):2914-2936
Phenols are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potential antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. The objective of this study was to investigate a suitable method for determination of protocatechuic acid, 4-aminobenzoic acid, chlorogenic acid, caffeic acid, vanillin, p-coumaric acid, rutin, ferulic acid, quercetin, resveratrol and quercitrin from apricot samples. A high-performance liquid chromatograph with electrochemical and UV detectors was used. The method was optimized in respect to both the separation selectivity of individual phenolic compounds and the maximum sensitivity with the electrochemical detection. The lowest limits of detection (3 S/N) using UV detection were estimated for ferulic acid (3 μM), quercitrin (4 μM) and quercetin (4 μM). Using electrochemical detection values of 27 nM, 40 nM and 37 nM were achieved for ferulic acid, quercitrin and quercetin, respectively. It follows from the acquired results that the coulometric detection under a universal potential of 600 mV is more suitable and sensitive for polyphenols determination than UV detection at a universal wavelength of 260 nm. Subsequently, we tested the influence of solvent composition, vortexing and sonication on separation efficiency. Our results showed that a combination of water, acetone and methanol in 20:20:60 ratio was the most effective for p-aminobenzoic acid, chlorgenic acid, caffeic acid, protocatechuic acid, ferulic acid, rutin, resveratrol and quercetin, in comparison with other solvents. On the other hand, vortexing at 4 °C produced the highest yield. Moreover, we tested the contents of individual polyphenols in the apricot cultivars Mamaria, Mold and LE-1075. The major phenolic compounds were chlorgenic acid and rutin. Chlorgenic acid was found in amounts of 2,302 mg/100 g in cultivar LE-1075, 546 mg/100 g in cultivar Mamaria and 129 mg/100 g in cultivar Mold. Generally, the cultivar LE-1075 produced the highest polyphenol content values, contrary to Mold, which compared to cultivar LE-1075 was quite poor from the point of view of the phenolics content. 相似文献
67.
Miroslava ?pérová Petr Nasadil Alena Pr??ová Ji?í Ku?erík 《Journal of Thermal Analysis and Calorimetry》2012,110(1):71-76
The degree of polymerization is one of the main parameters reflecting cellulose ageing. Viscometry is a method frequently used for determination of cellulose fibers polymerization degree, however, sample preparation and viscosity measurement are demanding, time consuming and do not provide reproducible results. In this study, the relationship between polymerization degree of cellulose fibers obtained by viscosity measurement and their degradation parameters obtained by thermal analysis were investigated. Differential scanning calorimetry provided values of effective combustion heat and thermogravimetry (TG) was used for the determination of temperatures and associated mass losses during the cellulose degradation. Effective combustion heat did not show any correlation with degree of polymerization of investigated cotton fabrics. In contrast, results from TG suggested several promising nonlinear correlations which could be used as a hint to develop a method useful for quick determination of cotton fabrics polymerization degree. The most promising correlations with cellulose polymerization degree were found for both rates of thermal and thermo-oxidative degradations. 相似文献
68.
Miroslava Trchová Zuzana Morávková Ivana Šeděnková Jaroslav Stejskal 《Chemical Papers》2012,66(5):415-445
Any surface immersed in the aqueous reaction mixture used for the preparation of polyaniline becomes coated with a polyaniline
film of submicrometre thickness. In this way, various materials can be modified by an overlayer of conducting polymer. The
present review illustrates the role of infrared, Raman, and UV-VIS spectroscopies in the studies of polyaniline film growth.
Spectroscopic methods are crucial in the evaluation of the performance of polyaniline films alone or in combination with nanoparticles
of noble metals. The assessment of film ageing and stability can be followed conveniently by these methods. Carbonization
of polyaniline films to nitrogen-containing carbon analogues is also discussed. 相似文献
69.
Petr Slaný Miroslava Pokorná Zdeněk Stuchlík 《General Relativity and Gravitation》2013,45(12):2611-2633
Equatorial circular orbits of test particles in the Kerr–anti-de Sitter black-hole and naked-singularity spacetimes are analyzed and their properties like the existence, orientation and stability are discussed. Due to the attractive cosmological constant ( $\varLambda <0$ ), all particles moving along equatorial orbits are still bound in the gravitational field of the central object. In general, there are two families of equatorial circular orbits. Particles moving along minus-family orbits possess negative angular momentum and, thus, they are counterrotating from the point of view of the locally non-rotating frames (LNRF). Particles moving along plus-family orbits possess, in most cases, positive angular momentum and belong to corotating particles from the point of view of the LNRF. Nevertheless, in stationary regions inside black holes and also near naked singularities with appropriately chosen value of the cosmological constant and rotational parameter $a<1.299$ , there are also counterrotating plus-family circular orbits. Moreover, in spacetimes with $a<1.089$ , some of these orbits are characterized by negative specific energy, indicating the bounding energy of the particle, moving along such an orbit, higher than its rest energy. In black-hole spacetimes, all such orbits are radially unstable, but in naked-singularity spacetimes, stable counterrotating orbits with negative specific energy exist. 相似文献
70.
Zuzana Repická Miroslava Puchoňová Lucia Husáriková Jan Monco Marián Koman Milan Mazúr Dušan Valigura 《Central European Journal of Chemistry》2012,10(5):1506-1515
The syntheses and characterizations of salicylatocopper(II) complexes of the formula Cu(X-sal)2(2-pyme)2 (X = 3-MeO (1), 4-MeO (2), 3-Me (3), 4-Me (4) and 5-Me (5), where 3-MeOsal− = 3-methoxysalicylate, 4-MeOsal− = 4-methoxysalicylate, 3-Mesal− = 3-methylsalicylate, 4-Mesal− = 4-methylsalicylate, 5-Mesal− = 5-methylsalicylate anion, and 2-pyme = 2-pyridylmethanol) are reported. The composition was determined by elemental analysis, and ligand coordination modes have been determined by spectroscopic methods (IR, UV-VIS). The crystal structure determination of [Cu(3-MeOsal)2(2-pyme)2] (1) and [Cu(5-Mesal)2(2-pyme)2] (5) have confirmed conclusions originally based on spectral data. EPR measurements of frozen water/methanol solutions containing different copper(II): 2-pyme molar ratios have indicated presence of complexes with only two nitrogen donor atoms bonded to each central atom. 相似文献